Which of the following best describes an outlier?

An outlier is best described as a score that significantly differs from other data points. This characterization is crucial because outliers can heavily influence statistical analyses, such as the mean and standard deviation, potentially skewing the results.

Understanding why this definition is important lies in recognizing the behavior of data in sets. Outliers represent extreme values that do not follow the overall trend of the data. For example, in a set of test scores where most students score between 70 and 90, a score of 30 would stand out as an outlier due to its significant deviation. Identifying such outliers helps in assessing the validity and reliability of conclusions drawn from the data, as they may not reflect the group's general pattern.

The other choices do not capture the essence of what an outlier represents or misinterpret its impact within a dataset. A score close to the mean would be typical data, while the most frequent score refers to mode, and a score that strongly affects calculations relates to the implications of being an outlier rather than a definition.